. If the weather had been better , we could have had a picnic .But it ___all day.
| A．rained | B．rains | C．has rained | D．is raining |
It rained that day and ___ the baseball game was called off.
| A．however | B．still | C．so | D．consequently |
It is not until the disease has progressed to AIDS ____a person begins to look sick.
| A．who | B．that | C．where | D．before |
It is not clear ____the effects of global warming will be.
| A．how | B．which | C．that | D．what |
All the scientific evidence ______ that increasing use of carbon dioxide ______ the rise of the earth’s temperature.
| A．show; result in | B．shows; result from |
| C．shows; results in | D．shows; results from |
Without the ‘ greenhouse effect’, the earth ____ be about thirty-three degrees Celsius cooler than it is.
| A．should | B．would | C．will | D．must |